A cermet sintered body, which comprises a hard phase mainly comprising a carbonitride of Ti and a 4a, 5a, 6a Group element component other than Ti (V, Cr, Zr, Nb, Mo, Hf, Ta and W), the hard phase being bound with a binder metallic phase mainly comprising Ni and/or Co is known. Such bodies have excellent plastic deformation resistance, etc. in comparison to hard alloys which have also been conventionally used. Therefore, the sintered bodies are replacing the super-hard alloys as a main stream cutting tool.
However, the cermet sintered bodies described above generally exhibit an appearance having a near black hue or color. Therefore, when wear proceeds as a tool is used, it is difficult to distinguish between a worn part and a non-worn part with the naked eye. Accordingly, problems may occur in that machining may proceed even when the life of the tool has expired. This may result in damage to the material which is being cut. On the other hand, a tool that can still be used may be replaced due to a misjudgment in the life of the tool by an operator.
An object of the present invention is to provide an improved cermet tool wherein the differences in color or hue between a worn part and non-worn part can be easily seen by the naked eye, so that the time at which the life of the tool is expired can readily be determined.